Rectifier.



G. W. PICKARD.

' RECTIFIER.

APPLICATION FILED NOV. 21. 1908.

' Patented May 15,1917.

f In ventor iclfiqrz'z' v away UNITED STATES OFFICE. I

GREENLEAF WHITTIER PIOKARD, OF AMESBURY, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPECIALTY APPARATUS COMPANY, OF NEW YORK, N. Y., A CORPORATION or NEW YORK.

' RECTIFIER.

Specification of Letters Patent. Patented May 15, 1917'.

Application filed November 21, 1908. Serial No. 463,769.

' ments in Rectifiersthe principles of which are set forth'in the followingspecification and accompanying drawing, which disclose the form of the invention which I now consider to be the best of the various forms in which the principles of the invention may be embodied.

This invention relates to rectifiers of oscillating or alternating currents, as oscillation detectors used as in wireless telegraphy and telephony, of the class embodying conductors which when connected in circuit between .substantially perfect 'minute and relatively large contacts, possess the property of rectifying such currents,such conductors also generally possessing highelectrical resistivity and thermo-electric power. The object is a more efficient device of this general class;

The-invention is embodied in the accompanying disclosure and is specified in the claims.

Of the drawings Figures 1 and 2 are diagrammatic illustrations of apparatus emplo'yed in successive stages of the process of manufacture,-and Fig. 3 is a perspective view of the completed device, with diagrammatic illustration of circuits and auxiliary.

apparatus showing the invention in operation. V 1

One of the principal features of the invention is based on the fact, observed by me, that the rectifying efficiency of conducting substances of this. class is greatly increased, (under other conditions hereinafter specified), by the application of a small steady or direct current of a definite order of magnitude and a uniform direction defined by coincidence with the direction of the effective direct current flow resulting from the rectilication of the oscillating current, said operative magnitude and direction being substantially defined, for any given rectifying substance, by predetermination of the. cor-v responding characteristics thereof.

A. fragment of any conductor surmised to possess rectifying properties, such as thosecontact with a supporting conductor C, such as a metallic cupcontaining more readily fusible metal F in which X'may be partially embedded. Since different conductors of this class have different directions of effective rectification action, in accordance with my observations, the direction for the specific conductor selected is first determined, as by testing for the direction of current flow through it, from a source of direct current of low E. M. F which results in maximum current, thatdirection being the one of effective rectification of oscillating currents. To further prepare for the test, X is connected in circuit with battery B, (Fig.

1), as a single ordinary dry cell of one and -or of any particular size, but simplylarge relative to the minute contact Y between X and Z, but is usually quite large, as shown, being with substantially the entire surface of the embedded portion of X. Since the rectification property of conductors of. the

rectifying class is rarely aelolotropic i,t is immaterial as to which part of the surface X contacts with F in C; and since the size of contact with the non-exposed part of 'X (in F) is immaterial provided that it be larger than that of the contact Y with the exposed part, therefore the size of thecircuit contact of the battery with support C is immaterial.

llla'nipulation of reversing switch S, (Fig. A

1), to apply the E. M. F. of battery B in opposite directions, Will readily show, by the galvanometer G, the direction of maximum rectification of conductor X, as that is the one which provides the greater deflection of the galvanometer needle.

Assume the material selection to be 'zincite or the oxid of zinc of my U. .S. Patent 886,154 of April 28th, 1908. If this be placed as at X (Fig. 1), and a rough surface such as a fracture face be exposed for contact with the other side of the circuit at Y, a suitable small contact, such as one at one of the minute projections from the rough surface, will be presented for operative contact irrespective of the use of a small-ended conductor such as Z. The direction of maximum rectification of this conductor I have observed to be as indicated by the arrows (Fig. 1), 2'. 0., from the positive or carbon pole Z) of battery B, through minute contact Y into X. The importance of this determination of direction is indicated by my observations that even if the superposed E. M. F. be applied in a magnitude predetermined in accordance with this invention, (as hereinafter specified), a wrong direction will actually decrease the efficiency as compared with a case where no E. M. F. at all is applied; asin the case of zincite for example, where superposition in the wrong direction of E. M. F. of the predetermined magnitude, reduces the efiiciency as much as it is increased by an application of such magnitude in the predetermined direction. lVhen the rectifier silicon is substituted at X. and a polished surface is exposed for minute contact at X with the pointed wire Z, as in my U. S. Patents Nos. 836,531 of Nov. 20th, l906, and 888,191 of May 19th, 1908, the maximum rectification, as I have observed, in pursuance of the test of Fig. 1, will be in the direction 0 posite to that of the arrows, Fig. 1, z'. 6., the positive. or carbon pole b of battery B to and through cup C, fusible metal F and conductor X, and out to minute contact Y, in cases where the silicon is pure. Impurities in the silicon result not only in inferior devices, but also cause unreliable reversals in the direction of maximum rectification. In the case of oxid of zinc, the impurities in the zincite occurrence seem to produce no effect different from that of the pure oxid. When the rectifier molybdenite of my U. S. Patent No. 904,222 of Nov. 17th, 1908, is substituted at X, in contact at Y with Z, its maximum rectification, as I have observed, in pursuance of the test of Fig. 1, will be from the positive or carbon pole b in a direction opposite to that of the arrows (Fig. l), i. e., the same direction as in the case of pure silicon.

Having now determined the direction of maximum rectification (2'. 0., the direction of effective or greater "direct current flow resulting from rectification) of the particular substance oxid of zinc for example, and therefore having determined the proper direction in which to superpose the low direct current upon the oscillations, in accordance with the invention, the next step is to determine the optimum magnitude of the E. M. F. of the current to be superposed, in the case of any particular rectifying substance undergoing test, and for the particular use to which the device is to be put, such as the reception of the feeble oscillations of wireless telegraphy and telephony. For I have found that each different substance which may be operatively placed at X, of the many which possess the requisite properties, has its own peculiar characteristic which demands a special and characteristic magnitude of superposed direct E. M. F., as well as a critical direction of application. the only peculiarity common to all such conductors being that optimum efiiciency is obtained by directing the superposed direct current coincidently with the direction of maximum rectification by the substance, as predetermined in pursuance of the test of Fig. 1. In the case of most substances, the magnitude of the superposed E. M. F. is very low, as of the order of a few hundredths of a volt, although in some less usual cases, it may be as large as' a volt, and in very exceptional cases even larger. In the case of all rectifying substances, however, the superposition of the critical E. M. F., when in the direction above specified for all cases, (relative to the direction of maximum rectification characteristic of the particular conductor), results in greatly increasing the efliciency of rectification; as for example in the case of oxid of zinc, pure or in the zinciteoccurrencc, the increase is nearly seventy-five per cent. over a case where the same substance has no superposition of direct E. M. F. on the oscillations. I have found also that a material increase of E. M. F. beyond the characteristic magnitude predetermined for a given substance, causes a proportionately rapid falling off in efiiciency; as for example in the case of oxid of zinc in either its pure form or its zincite occurrence, a superposed E. M. F. of a magnitude even as large as only one volt, and

even in the predetermined direction of maximum rectification, will result in substantial moperativeness, i. 0., as contrasted with the considerable efficiency when no E. M. -F. at all is superposed. I have found also, as indicated hereinbefore, (and as now specifically emphasized by the case of zincite, the efliciency of which is increased nearly seventyfiveper cent. by a superposition of the predetermined E. M. F. in the predetermined direction), that the efliciency is reduced by an application in a direction opposite to that of predetermination of even the predetermined magnitude, in substantially the'same ate as the elliciency is increased by'an application in the predetermined direction.

The above indicates the importance of predetermining the peculiar and characteristic magnitude of the superposed E. M. F., as well as its direction, as the value for a given substance; This predetermination of characteristic magnitude may be made with the apparatus of Fig. 2, wherein oscillations are supplied for testing purposes from any suitable source 1, 2, and through an oscillation transformer T. As shown at positive pole band negative pole at of battery B and by the arrows, the zincite X is being 'supplied With-current in the same direction as that found with the test set of Fig. 1 to be that of maximum rectification. In the test of Fig. 2 the zincite X is properly tested with some indifferent or non-rectifying conductor, as Z which may be copper for example, held in supporting cup G by being embedded in the more readily fusible metal F arough surface of Z contacting-with the rough surface of X to obtain an operative minute and substantially perfect contact between the two such as that at Y, Fig. 1. In the test set of Fig. 2 the battery 13, telephone R, condenser K and potentiometer P are connected as shown, and the -E. M. F is varied by manipulation of mov- ".operating rectifying conductors instead of one such conductor in combination with a non-rectifying contacting conductor, there appear above two different coiiperating rectifying conductors for the oxid of zinc; be cause, although silicon and molybdenite each has a different direction of maximum rectification relative to said oxid (and approximately the same order of value of magnitude of applied EfM. F.), yet on account of such opposite direction. either of said conductors, according to theory, cooperate with said oXid because when put in operative contact therewith the effective joint rectification is in a common direction.

. I- have found that the tests of Figs. 1 and 2 applied to chalcopyrite show that its values are substantially thesame as those of said oxid, not only as to magnitude of applied E. M. F., but as to direction. For example, asto magnitude, under the same conditions as said oxid, the chalcopyrite has a value of approximately five one hundredths of a volt,' but' its same direction of maximum rectification as oxid of zinc, would not according to theory,'make 1t. a suitable conductor for coiiperation therewith. However, contrary to theory, and probably on account of some peculiar characteristics of chalcopyrite not understood, and notwithstanding its like direction of rectlfication,

Condenser K has a ca-' test shows it to be an admirable conductor for cooperation with oxid of Zinc. Chalcopyrite, as well as silicon and molybdenite,

is operative in the main invention claimed herein, wherein it acts substantially as a non-rectifying or indifierent conductor. If desired, in any case, after the test of Fig. 1 has shown two conductors to have opposite values as to direction, and in case the test of each with Fig. 2. shows some divergence between their respective values as to magnitude of applied E. 'M. F, then both said conductors may be subjected simultaneously to the Fig. 2 test, in order to adapt them in a given device for best value for commerce. Thus, if the Fig. 2 test of given samples of oxid of zinc. and of silicon for example, made separately for each one with a non-rectifying conductor at Z shows a divergence between their .values of magnitude, the latter may be placed at Z and the former at X, and the testof Fig. 2 repeated,

to determine the particular value for those two special samples of thetwo named substances.

By this method, measurements of numbers of selections of zincite under otherwise constant conditions except potentiometer variations, will give the working average optimum va ue for the superposed E. M. F. for all probable selections of that substance as an example. or zincite'l have found this characteristic-value to be from five to ten one hundredths of a-volt, this being obviously very low. For silicon (when pure, direction reverse relative to zincite) I have found it to be between tenand fifteen one hundredths of avolt; and for molybdenite (direction reverse to zincite) I have found it to be between fifteen and twenty-five one hundredths of 9. volt. These values apply to cases where feebly damped oscillations are employed. With less feebly damped waves, the values may increase to limits approximately double those named, and in employing the invention in pursuance hereof the matter of persistency or damping of the received wave trains should therefore be taken into consideration.

In conducting the predetermination tests of Figs 1 and 2, the convenience is manifest which results from fixing conductor X as by the fusible metal F in support C, whereby after making the first test, Fig. 1, the exposed surface of .X may be connected to thepositive pole of the battery B, Fig. 2, without question, and-without other marking for identification. This matter of con venience will be seen to be an essential in the construction of the detector itself, now to be lation; transformer T and variable air condenser D being arranged as shown as well,

known in wireless telegraphy, and connected to detector binding posts 3, 4. The cup C is removably held by screw 5 in support ng post 5, said post being connected to bind ng post 3 as shown, the complete detector being mounted on a suitable insulating base A. The cup 0 is carried on the end of a rod E loose in a sleeve G containing a helical spring (not shown) pressing rod E toward the left to force. cup C and conductor Z against X to produce a substantially perfect minute contact Y therewith. This contact will be effectively minute, with the rough surface of conductor X shown (conductor Z having a generally pointed form so that the pointed end makes contact at Y) and is the smaller of the two circuit contacts of X, the other and larger being that with the fusible metal F and cup C. Sleeve G is adjustably fixed in part H, which in turn is swiveled on part I. As shown, a screw enters down through block H to fix sleeve G in its adjustable position. The helical spring, not shown, surrounds an intermediate part of the rod E, the right-hand end of the rod being of smaller diameter than the left-hand end, and the spring bearing to the left against the left-hand or larger diametered part of therod E. The spring is held in place at the right by the end of sleeve G. In the position of adjustment in which sleeve G is shown, the spring is in an intermediate state of compression. If sleeve G be moved farther to the left, the spring will be ut under greater compression. This adjustment of sleeve and spring is a more or less permanent one, i. 6., it is substantially permanent for a given sample of sensitive materials X and Z and after the best adjustment for the same is once made, it will usually not be desirable to change it. The adjustment for contact selection is however, adopted for frequent and very quick change, in order to permit substantially instantaneous readjustment to operative condition in case of the occurrence of inoperative conditions in the midst of the receipt of a message. This adjustment is by the handle at the right, and involves three kinds of movement of the support, 2'. e., reciprocating,revolving and rotary. The freedom for reciprocation per mits manipulation of the handle to withdraw Z away from the uneven surface of X, and also permits the spring to. push it back thereafter when the operator has ceased pulling on the handle and while continuing to hold the handle yet permits the spring to act so as to cause Z to move back gradually to X. The freedom for the revolution of the entire structure mounted on block I,' permits the movement of Z in a horizontal plane to select any contact along a horizontal line across X. The freedom of rotation of rod E on its own axis and inside of sleeve G, coupled with the mounting of Z in the fusible metal in cup G which mounting is eccentric to the axls of rod E, permits Z to select any contact tact of adjustment at the time of commencement of a message, becomes inoperative during the receipt of a message, and if the operator does not thereupon succeed at once in selecting a good operative contact, he may make several new contacts in quick succes' sion until he strikes a suitable contact. Usually, in such adjustments, the reciproeating motion of rod E is also revolved with the movements of revolution and rotation. In any case, after Z has been moved to a position opposite to a different point of contact on X, the operator relaxes his pull on the operating handle and permits the helical spring to push rod E, etc., to the left to effect the new contact, the effectiveness of which will be determined by the phones H The lower side of condenser D is connected, through binding post 4, to one ter minal 6 of a telephone R. A small fixed value mica-condenser K is shunted around R and around the reductor P, P, and may be located in any suitable manner inside the base A, as indicated by the dotted lines. The battery B (consisting of a single common dry cell of approximately one and one-half volts) is connected to P,.P as shown, and as to direction predetermined in accordance with the invention, whereby, in the case of zincite for example, the negative or zinc pole a of the battery is connected to X through posts 8, 7 6, 4 and 3, so that the battery current flows in the opposite direction from the positive or carbon pole b, as indicated by the arrows, through post I, the reductor, conductor Z and minute contact Y into X, i. 6., in the predetermined direction of maximum rectification 'for zincite. The reductor P, P, effects the object of the invention as to the predetermined ofiier of magnitude of the superposed E. M. F., by reducing the E. M. F. of the battery to that very low value (five one hundredths of a volt) predetermined for zincite in the predetermined direction of maximum rectification. Thereductor P, P is constructed and arranged for that purpose as follows. P and P are a pair of ordinary resistances such as iron wire, pro ortioned in the ratio of one to twenty-nine, being the smaller. The potential existing across the terminals of P is one-thirtieth of that of the 1,225 ,eee

battery B, for the reason that the sum of P and P is thirty timesthat of P Since the battery is of one and a half volts, the potential across P being one thirtieth of that, is

five one hundredths of :1 volt, which, with the connections as shown, is the potential of applied E. M. F. may be that'which was predetermined by the Fig. 2 test for a given pair of selected. conductors and tore given condition of persistency of oscillations. In case it is desired to operate the oxid of zinc detector at its efliciency of higher superposed E. M. F., 2'. e., ten one hundredths of a volt,

it is not necessary to modify or alter the reductor P 2?, as the object can be obtained by constituting battery B of two ordinary dry cells of one and a half volts each and that, with the reductor as above, will double the voltage around X. For skilled operators the reductor may consist of a potentiometer like P (Fig. 2) adapted to permit the detector to be operated at any degree of potential substantially within the limits of the order of magnitude of five and ten one hundredths of 9. volt; or otherwise in the case of other substances, the values for the characteristic order of magnitude being predetermined in pursuance of the above described methods and in accordance with the invene tion.

In connection with the fixation of conductor X in'the fusible metal F, in cup C;

. and when the cup, with its contents, is re placed by a duplicate repair part thefixw' tion means for conductor X insures that the exposed surface, (2'1. e., the minute contact side) of that cenductor will be placed in contact with the positive side of the battery circuit; and so in the cases of other substances,

the values at which are to be predetermined in accordance with the invention.

I claim: v

1. In an oscillation detector, the combination with a rectifying conductor of the class described and a contacting conductor therefor, of a rotatable support for one of said conductor being said conductors,

to the axls of 1ts sald supmounted eccentric port. p 2. In an oscillation detector, the combination with a rectifying conductor of the class described and a contacting conductor therefor, of a-support for one of said conductors, said support-consisting of a re ciprocating and rotating arm, said conduc tor being mounted eccentric to the axis of rotation of said arm.-

3. In an oscillation detector, the combination with ajrectifying conductor of the class described and a contacting conductor therefor, of a supportfor one of said conductors, said support consisting of a recip- I rocating, swinging and rotating arm, said conductor being mounted eccentric to the axis of rotation of the arm.

4. In an oscillation detector, the combination with a rectifying conductor of the class described and a contacting conductor therefor,-of a support for one of said conductors, said support consisting of a rod, and a sleeve in which the rod is rotatable; said conductor being mounted eccentric to the axis of rotation of the rod.

5. In an oscillation detector, the combination with a rectifying conductor of the class described and a contacting conductor therefor, of a support for one of said consieeve in which the rod is rotatable, said conductor being mounted eccentric to the axis of rotation of said rod, and a swiveled support for said sleeve.

6. In an oscillation detector, the combination with a rectifying conductor of the eiass described and a contacting conductcr therefor, one of said conductors being nor-' mally fixed; of a support fer the other and adjustable conductor. said support ecnsist ing of a rod, said adjustable conductor being mounted eccentric to the axis at rota-- tion of the rod; and a swivei support for the rod in which the latter is reciprecabie and rctatable.

7'. in an oscillation detector, the cor-abination with a rectifying conductor of the class described, and a contacting conductor therefor, of a rotatable snppcrt for ens said conductors; one of said ccnductors ing mounted cccentricaiiy to the axis of rotation of said support, whereby the rctation of the support permits contact selection along a circular'path on the surface cit cne of said conductors.

GREENLEAF WEETIER Pifiiiiiiiit. Viitnesses:

EDWARD H. Rowena, I Bmnorrn 'B. Knunara. 

